	
	import delimited using $FILEPATH-CRIME-SHIFT, clear
	
	* Identify month-shift
	gen year_month = substr(date,1,4) + substr(date, 6,2)
	destring year_month, replace force
	recode hour (23 = 1) (0/6=1) (7/14 = 2) (15/22 = 3), gen(watch)
	
	collapse (sum) all_crimes violent_crimes (mean) population = b01001_001e, ///
	by(year_month district watch)
	
	gen mod_strata = 1000 * district + watch
	
	save ${CRIME-SHIFT-data}, replace